Heretofore, level control sensor switch mechanisms have been used which are mountable upon a bin containing bulk material of varying levels and wherein, a low speed electric motor within the sensor housing is adapted to continuously drive a paddle when out of contact with bulk material within the bin and which motor will stall when the level of bulk material within the bin reaches the paddle impeding its rotation.
Various types of signal mechanisms have been heretofore used which respond to the stalling of the motor due to the level of the bulk material. One characteristic of prior art devices is that there may be a false signaling of the material level in the bin due to product surges during filling or emptying of the bin.
Another problem with pre-existing devices is the lack of sensitivity of the control mechanism depending upon the density of the material stored within the bin and dispensed therefrom. Heretofore, it has been necessary to increase or decrease the size of the paddle areas, making the unit more or less responsive to bulk material levels.
Heretofore, with the level control sensor mechanism being used in conjunction with chemicals and other particulate materials, some of which may be corrosive, there has been damage to the moving parts of the sensor mechanism including the drive shaft and paddle, particularly to metal parts exposed within the bin.
Heretofore, furthermore, since the particulate materials may be of fine grain, there has been the problem of some of the material moving along the drive shaft and into the housing, damaging bearings and the motor.
Another problem which has existed with pre-existing devices is that they have been limited to the number of switch mechanisms which may be controlled by the sensor.
Heretofore, in the use of switch mechanisms, spring-loaded switch arms were employed for pushing the motor actuating arm away from the switch when the rotating paddle was free of the material.